This is a psychophysical investigation of the mechanisms involved in the perception of spatial patterns by normal, human viewers. The results of recording from single cells in the visual system and the results of recent psychophysical experiments have led to a widely entertained model of pattern vision, often called the multiple-tuned-channel model. The research elaborates the model in three ways. (1) It seeks to define the response ranges of bandwidths of the channels with respect to orientation, spatial frequency, and phase or location. Models are being developed which permit bandwidths to be estimated from comparison of detection and discrimination data. (2) It seeks to use the model to describe the changes in visual organization and capacity which occur as a function of retinal eccentricity and light adaptation. (3) It explores the nature and extent of inhibitory interaction between channels. Adult subjects with normal vision are used. Detection and discrimination tasks are used.